Chromosomes (from yeasts) have peculiarly repeated poly GT tracts at their ends (the telomeres) suggesting that the "Z" DNA configuration may be involved. The in vitro DNA replication system of N4 bacteriophage has been shown to require an exonuclease, polymerase and DNA-binding protein. In vivo, replication seems to occur via strand displacement. The mechanism of action of the catalytic antitumor antibiotic, alpha saracin, has been determined. This information is particularly important for understanding the structure of the eucaryotic ribosome. We have completed further work demonstrating the role of replication in the movement of transposable genetic elements, have cloned some of the (yeast) genes involved in meiosis and have continued studies on "suicide" inhibitors of enzymes involved in nucleotide biosynthesis. It has been shown that a mechanism controlling the repair of mutagenic damage produced by alkylating agents is epigenetic although chromosomally based.